[SPARK-13874][DOC] Remove docs of streaming-akka, streaming-zeromq, streaming-mqtt and streaming-twitter

## What changes were proposed in this pull request?

This PR removes all docs about the old streaming-akka, streaming-zeromq, streaming-mqtt and streaming-twitter projects since I have already copied them to https://github.com/spark-packages

Also remove mqtt_wordcount.py that I forgot to remove previously.

## How was this patch tested?

Jenkins PR Build.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #11824 from zsxwing/remove-doc.

1 files changed, 1 insertions, 6 deletions

diff --git a/project/MimaBuild.scala b/project/MimaBuild.scala
index acf7b8961e..3dc1ceacde 100644
--- a/project/MimaBuild.scala
+++ b/project/MimaBuild.scala
@@ -88,16 +88,11 @@ object MimaBuild {
 
   def mimaSettings(sparkHome: File, projectRef: ProjectRef) = {
     val organization = "org.apache.spark"
-    // The resolvers setting for MQTT Repository is needed for mqttv3(1.0.1)
-    // because spark-streaming-mqtt(1.6.0) depends on it.
-    // Remove the setting on updating previousSparkVersion.
     val previousSparkVersion = "1.6.0"
     val fullId = "spark-" + projectRef.project + "_2.11"
     mimaDefaultSettings ++
     Seq(previousArtifact := Some(organization % fullId % previousSparkVersion),
-      binaryIssueFilters ++= ignoredABIProblems(sparkHome, version.value),
-      sbt.Keys.resolvers +=
-        "MQTT Repository" at "https://repo.eclipse.org/content/repositories/paho-releases")
+      binaryIssueFilters ++= ignoredABIProblems(sparkHome, version.value))
   }
 
 }